The present invention relates generally to plasma cutting systems and, more particularly, to an inverter powered plasma cutting system with automatic gas flow control.
Plasma cutting is a process in which an electric arc and plasma gas are used to cut or gouge a workpiece. Plasma cutters typically include a power source, a gas supply, such as compressed air, and a torch. The torch is constructed to create and maintain the plasma arc. To generate the plasma cutting power, a power source receives an input voltage from a transmission power receptacle or generator and provides output power to a pair of output terminals. One of the output terminals is connected to an electrode and the other is connected to the workpiece. An air supply is used with most plasma cutters to carry and propel the arc to the workpiece and assist in cooling the torch.
Prior to operation of the plasma cutting system, an operator must manually set a regulator of the air flow system such that a desired air flow is provided during operation of the plasma cutting system. The air flow is set by the operator to correlate with the intended plasma cutting process. That is, the rate of air flow delivered to the plasma torch during a plasma arc process varies depending on the type of plasma processing. For example, the air flow required for plasma cutting may differ from that needed for plasma gouging. Although such in-field adjustment of the air flow provides an operator with more precision control of the air flow rate, such a construction is not without its drawbacks.
Operator control of the air flow invariably presents the opportunity for improper setting of the air flow control, especially by inexperienced operators. For example, in a dynamic work environment, an operator may be required to perform gouging and cutting operations in a relatively continuous manner. It may not be practical for the operator to sequentially perform all of the desired cutting processes and then all of the desired gouging process, or vice verse. The operator may be required to sequentially mix a plurality of cutting processes and a plurality of gouging processes. Suspending one process to reconfigure the power source for another process is time consuming and results in overall process inefficiency. In addition to configuring the air flow for the intended process, the operator must also configure the power source to deliver a desired power signal suitable for the intended process.
In addition to the inefficiency associated with the repetitive reconfiguring of the power source to deliver the appropriate power signal/air flow as dictated by the intended plasma process, the means for allowing operator control of the air flow complicates power source construction and expense. Generally, an adjustable air flow control must be made readily accessible to the operator. This is frequently achieved by passing a control dial of a regulator through an opening formed in the housing. Not only does the operator variable flow control occupy space in the interior of the power source thereby increasing the overall size of the plasma cutting device, the control must be placed on the front panel, thereby further limiting the internal configuration options. Alternatively, the such regulators have been located external to the power source. Obviously, there are drawbacks to these systems such as enabling the possibility of unregulated air to the power source if the regulator is bypassed, and simply requiring one more apparatus to the overall system.
In conjunction with the operator variable flow control, a gauge is also required to provide the operator with feedback as to the air flow setting. The pressure gauge must also be fluidly connected to the gas system and also requires another opening formed preferably in the front panel of the power source.
Further complicating construction of the plasma arc power sources, the gas must be allowed to flow without plasma arc power to allow the operator to accurately set the adjustable gas flow. Such operation requires that the power source have an operating mode wherein the plasma forming gas is allowed to flow but the power supply is disabled thereby preventing inadvertent formation of a plasma arc when the operator is setting the desired plasma gas flow. Providing such an operating mode further complicates the construction of the power source and increases the complexity of the device and the operation thereof.
It would, therefore, be desirable to design a plasma cutting system with simplified construction, operation, and control of the gas system.